Annular slot proportional jet amplifier for a fluidic sound generator

ABSTRACT

An annular slot proportional jet amplifier is disclosed in which an annular control jet is used to deflect an annular power jet from an annular receiver into a low pressure region to provide a high gain proportional jet amplifier. A fluidic sound generator is also disclosed utilizing an annular slot proportional jet amplifier, with the annular receiver coupled to a centerbody and horn radiator structure in order to provide high intensity sound generation.

United States Patent Teitelbaum [54] ANNULAR SLOT PROPORTIONAL JET AMPLIFIER FOR A FLUIDIC SOUND GENERATOR [72] Inventor: Bernard R.

mingham, Mich.

[73] Assignee: The Bendix Corporation Teitelbaum, Bir- [22] Filed: Sept. 14, 1970 [21] App1.No.: 71,711

[52] US. Cl. ..116/l37, 116/142, 137/610 [51] Int. Cl. ..B06b 3/00 [58] Field of Search ....1 16/137, 137 A, 142,142 FP; 137/815, 610

[56] References Cited UNITED STATES PATENTS 2,692,800 10/1954 Nichols et al.............l37/8l.5

3,039,490 6/1962 Carlson, Jr. ..l37/610 3,226,029 12/1965 Goodman et al...116/137 A X [451 0ct.3l,1972

3,405,724 10/1968 Goldschmied 137/8 1 .5 3,479,250 11/1969 Ripley ..137/81.5 X 3,499,458 3/1970 Korta et a1 ..l37/8 l .5 3,503,410 3/1970 Richards ..137/81.5 3,533,373 10/1970 King ..1 16/137 A Primary Examiner-Louis J. Capozi Attorney-John R. Benefiel and Plante, Hartz, Smith and Thompson [57] ABSTRACT An annular slot proportional jet amplifier is disclosed in which an annular control jet is used to deflect an annular power jet from an annular receiver into a low pressure region to provide a high gain proportional jet amplifier. A fluidic sound generator is also disclosed utilizing an annular slot proportional jet amplifier, with the annular receiver coupled to a centerbody and horn radiator structure in order to provide high intensity sound generation.

11 Claims, 4 Drawing Figures PAIENTEnncm m2 3.701 334 DTTORNEY 1 AMPLIFIER FOR A FLUIDIC SOUND GENERATOR BACKGROUND OF THE INVENTION 1. Field of the Invention This invention concerns a fluidic amplifier particularly suited for use with high intensity fluidically actuated sound generators.

2. Prior Art Fluidic amplifiers of the bistable jet type which utilize a generally annular power and control jet have been known in the prior art, as for example those described in US. Pat. No. 3,039,490 to Carlson, Jr., and US. Pat. No. 3,503,410 to Richards.

These devices have the advantage of eliminating corners, as must necessarily be present in planar jet amplifiers and the resultant turbulent flow, and also provide an amplifier having large port sizes in a compact space.

Furthermore, it has been found that staging of amplifiers made according to this configuration can be very conveniently carried out, particularly for amplifiers having large port sizes.

However, heretofore, these devices have involved switching between different states of wall attachment flow between a pair of outlets, and hence are somewhat limited in application, since flow in the outlets is either on or off and continuous modulation at an outlet is not possible.

This is a particular disadvantage in any attempt to utilize such a device in sound generation, as ready controllability of the output wave form of such a device is usually required for the purposes for which high intensity sound generators are currently being used, i.e., for simulating noise originating in the jet efflux of propulsion devices and the turbulent boundary layer of modern aerospace craft for research investigations, as well as for various other research purposes.

Conventional planar proportional jet amplifiers, in addition to not having the advantages cited above, do not usually exhibit sufficiently high gains to be feasible in these high intensity applications, particularly in the higher frequencies.

Such sound generators in the past have usually involved the use or sirens, but problems of wear and fatigue in the siren mechanism and drift of critical adjustments in the high power transducing stage have usually been encountered, increasing service and maintenance requirements. In addition, this approach also does not lend itself to ready controllability of the shape of the output waveform.

Therefore, it is an object of the present invention to provide a proportional jet amplifier capable of high gain performance, particularly under high frequency conditions.

It is another object of the present invention to provide a large port area proportional jet amplifier which is relatively compact and may be staged conveniently.

It is a further object of the present invention to provide a high intensity sound generator which is not subject to wear or fatigue, and which is substantially free from drift.

It is a further object to provide a sound generator capable of generating a readily controllable waveform shape.

, 2 SUMMARY OF THE INVENTION These and other objects which will become apparent on reading the following specification and claims are accomplished by providing an annularly configured proportional jet amplifier or a staged series thereof, driven by a low power generating device and coupled to a horn and centerbody to provide a high intensity controllable waveform sound output.

BRIEF DESCRIPT ION OF THE DRAWING FIG. 1 is a partially sectional and fragmental view of a fluidic sound generator according to the present invention.

FIG. 2 is a view of the section taken along the line 2-2 in FIG. 1.

FIG. 3 is a view of the section taken along the line 3-3 in FIG. 1.

FIG. 4 is a view of the section taken along the line 4-4 in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following detailed description certain specific terminology will be employed for the sake of clarity and a specific embodiment described in order to provide a clear understanding of the invention, but it is to be understood that the invention :is not so limited and may be practiced in a variety of forms and embodiments.

Referring to the drawings, and particularly FIG. 1, an annularly slotted jet amplifier 10 is depicted. This device includes an annular supply pressure region 12 connected to a source 14 via line 16, and a coaxial concentric control pressure region 18 connected to a signal source indicated schematically at 20. The source 20 may be any of a number of conventional electromechanical pressure generators such as loudspeaker drivers or could be the output of an earlier amplifier stage, since as discussed above, this amplifier configuration may be staged conveniently, or any other suitable source of an acoustical pressure flow signal.

Supply fluid is directed through an annular opening 22 towards a corresponding annular receiver passage 24 axially spaced and aligned therewith.

The control fluid jet is caused to diverge about its periphery by means of a conical deflector 26 so as to diverge and intercept the annular supply flow and cause it to be deflected outwardly, into a vent or low pressure region 25 to an extent depending on the relative momentums of the respective streams and the spacing d, the shim 58 thickness and angularity of the conical deflector 26. To an extent depending on the values of these parameters, this will cause a corresponding change in the flow received by the receiver passage 24, and for a given application these parameters may be adjusted to determine the optimum configuration in regards to gain and linearity of the device.

The spacing d may be set by the length of spacers 23 clamped between the housing members 27 and 29 by bolts 31.

The annular receiver passage 24 is formed by a pair of generally cylindrical centerbodies 28 and 30 disposed in corresponding bores 32 and 34 of housing members 36 and 38, and maintained in concentricity therewith by means of an annular flange 39 integral with centerbody 28 and clamped between the housing members 36 and 38. Openings 41 are milled in the flange 39 to create a portion of the annular receiver passage 24, leaving intermediate areas 40 to support the centerbody 28. Fairing elements 42 and 44 may be included for streamlining purposes. Vent passages 45 may also be provided to vent the area under the deflector 26 in order to nullify any tendency to create a deflecting pressure differential across the power jet. In actual practice, however, it is difficult to vent this space sufficiently to maintain it at atmospheric pressure due to the construction of the unit, which limits the size of any such passage.

Disposed in slots 46 arranged about the periphery of centerbodies 28 and 30, and circumferentially spaced are sets of fins 48 and 50 to aid in flow straightening and to prevent any standing circumferential acoustic waves in the receiver passage 24.

The deflector 26 is positioned by means of a rod 52 passing through centerbody 28 and 30 and threadedly engaging a reduced end portion 54 of the horn centerbody 56 to be described more fully herein. This secures the centerbodies 28 and 30, deflector 26, and horn centerbody 56 together. A shim spacer 57 serves to locate the axial position of the deflector 26 while retainer 60 axially retains the sets of fins 48 and 50.

As will be understood by those skilled in the art, this amplifier will produce pressure-flow variations in the receiver passage 24 inversely proportional to those of the control jet, but amplified to an extent depending on the gain of the amplifier. For this application, a substantially inversely proportional or linear relationship between control momentum and receiver flow and pressure is possible since the operating range is fairly limited, and by proper adjustment of the parameters described, this result is easily obtained.

In order to convert the pulsing pressure-flow exiting the annular receiver passage 24 into radiated acoustical energy, a horn assembly 58 is provided, including the centerbody 56 previously noted as well as an exponential horn member 60. The centerbody 56 is located with respect to the annular jet amplifier so that the annular receiver passage 24 is axially aligned with the diverging space 62 defined by the inner surface of the exponential horn member 60 and centerbody 56. This allows relatively efficient coupling of the amplified fluidic signal to the space at which the acoustical energy is to be directed.

in order to set the operating point of the amplifier at the optimum operating point for the alternating pressure-flow conditions to be encountered, a restriction 64 may be provided, which under d-c pressure-flow conditions provides maximum gainfor the amplifier at a point corresponding to a value intermediate the alternatin'g conditions encountered.

The details of the horn design may be arrived at by principles well known to those skilled in the art, and hence a detailed discussion thereof is not here included.

It can be appreciated that the annular receiver passage 24 allows a very compact and efficient physical coupling of the fluid amplifier l0 and the horn assembly 58 since it may be connected directly thereto, without radical transition sections.

It has been found that the annular slot configuration unexpectedly provides rather substantially higher gains both under static and alternating pressure-flow conditions compared to conventional planar proportional jet amplifiers, and hence is capable of satisfactorily yielding high intensity outputs for the sound generator unit.

As noted above, these units can also be easily staged to provide multiple levels of fluid amplification of the initial signal to provide very high intensity sound outputs from the horn assembly 58.

Furthermore, the nature of this approach, i.e., an electrical, magnetic, or electromechanical, etc., initial acoustical signal fluidically amplified by means of a proportional jet amplifier allows ready controllability of the particular sound waveform as compared with the siren approaches described above, or with bistable planar or annular jet amplifiers.

Hence, it can be appreciated that a low maintenance, controllable, high intensity sound generator has been provided with a relatively simple compact design, as well as an improved proportional jet amplifier. Indeed, for one configuration and load condition, pressure gains of four times or more over a conventional planar proportional jet amplifier were obtained.

While a specific embodiment has been described, it should be appreciated that many variations are possible within the scope of the invention. Furthermore, while the annularly configured proportional jet amplifier has been disclosed in combination with sound generating structure, and is particularly suited to this use, it may be used in other contexts and applications to advantage.

What is claimed is:

1. A proportional fluid jet amplifier comprising:

means for creating a substantially annular fluid power jet;

receiver means, including a substantially annular passage substantially aligned with said power jet to receive fluid flow from said power jet; and

control means directing an annular fluid control jet at said power jet;

means causing fluid flow from said power jet to deflect about its periphery from said receiver means passage to cause a variation in flow therein substantially proportional to the magnitude of the deflecting momentum of said control jet.

2. The amplifier of claim 1 wherein said means caus ing said power jet to be deflected includes means causing said control jet to diverge outwardly about its periphery so as to intercept said power jet upstream from said receiver means passage.

3. The amplifier of claim 1 wherein said means causing said power jet to be proportionally deflected includes a low pressure region extending about the power jet periphery into which the power jet may be deflected.

4. The amplifier of claim 2 wherein said means causing said control jet to diverge includes a conical deflec tor disposed axially aligned with respect to said power jet and receiver means passage.

5. The amplifier of claim 1 wherein said receiver means includes a plurality of fins disposed circumferentially spaced in the receiver means passage, whereby standing circumferential acoustic waves may be prevented.

6. A fluidically actuated sound generator comprising:

supply means for creating an annular fluid power jet;

receiver means including an annular passage aligned therewith disposed to receive fluid from said power jet;

control means providing a fluid control jet directed 5 to deflect said power jet about its periphery from said receiver passage, including means for pulsing said control jet momentum to create an amplified acoustical variation of pressure and flow in said receiver passage;

a horn assembly including a diverging horn section and a concentric centerbody disposed therein defining for at least a portion of said horn section an annular diverging passage; and

means creating a fluid connection between said receiver passage and said horn annular passage, whereby said control jet pulsing creates an amplified acoustical signal in said receiver passage which is efficiently coupled to a space at which the acoustical energy is directed by said horn assembly.

7. The sound generator of claim 6 wherein said control means includes means deflecting said power jet substantially proportionally to the momentum of said control jet.

8. The sound generator of claim 7 wherein said means deflecting said power jet substantially proportionally to said control jet momentum includes a low pressure vent region extending about the periphery of said power jet upstream from said receiver means passage into which said power jet may be deflected.

9. The sound generator of claim 7 wherein said control jet means includes means causing said control jet to diverge outwardly about its periphery so as to intercept said power jet upstream from said receiver means passage.

10. The sound generator of claim 9 wherein said means causing said control jet to diverge includes a conical deflector disposed axially aligned with respect to said power jet and receiver means passage.

11. The sound generator of claim 10 wherein said receiver means includes a plurality of fins disposed circumferentially spaced in the receiver means passage, whereby standing circumferential acoustic waves may be prevented. 

1. A proportional fluid jet amplifier comprising: means for creating a substantially annular fluid power jet; receiver means, including a substantially annular passage substantially aligned with said power jet to receive fluid flow from said power jet; and control means directing an annular fluid control jet at said power jet; means causing fluid flow from said power jet to deflect about its periphery from said receiver means passage to cause a variation in flow therein substantially proportional to the magnitude of the deflecting momentum of said control jet.
 2. The amplifier of claim 1 wherein said means causing said power jet to be deflected includes means causing said control jet to diverge outwardly about its periphery so as to intercept said power jet upstream from said receiver means passage.
 3. The amplifier of claim 1 wherein said means causing said power jet to be proportionally deflected includes a low pressure region extending about the power jet periphery into which the power jet may be deflected.
 4. The amplifier of claim 2 wherein said means causing said control jet to diverge includes a conical deflector disposed axially aligned with respect to said power jet and receiver means passage.
 5. The amplifier of claim 1 wherein said receiver means includes a plurality of fins disposed circumferentially spaced in the receiver means passage, whereby standing circumferential acoustic waves may be prevented.
 6. A fluidically actuated sound generator comprising: supply means for creating an annular fluid power jet; receiver means including an annular passage aligned therewith disposed to receive fluid from said power jet; control means providing a fluid control jet directed to deflect said power jet about its periphery from said receiver passage, including means for pulsing said control jet momentum to create an amplified acoustical variation of pressure and flow in said receiver passage; a horn assembly including a diverging horn section and a concentric centerbody disposed therein defining for at least a portion of said horn section an annular diverging passage; and means creating a fluid connection between said receiver passage and said horn annular passage, whereby said control jet pulsing creates an amplified acoustical signal in said receiver passage which is efficiently coupled to a space at which the acoustical energy is directed by said horn assembly.
 7. The sound generator of claim 6 wherein said control means includes means deflecting said power jet substantially proportionally to the momentum of said control jet.
 8. The sound generator of claim 7 wherein said means deflecting said power jet substantially proportionally to said control jet momentum includes a low pressure vent region extending about the periphery of said power jet upstream from said receiver means passage into which said power jet may be deflected.
 9. The sound generator of claim 7 wherein said control jet means includes means causing said control jet to diverge outwardly about its periphery so as to intercept said power jet upstream from said receiver means passage.
 10. The sound generator of claim 9 wherein said means causing said control jet to diverge includes a conical deflector disposed axially aligned with respect to said power jet and receiver means passage.
 11. The sound generator of claim 10 wherein said receiver means includes a plurality of fins disposed circumferentially spaced in the receiver means passage, whereby standing circumferential acoustic waves may be prevented. 